Typically, for example only, many dialysis medical patients are treated for a few hours every two or three days. Dialysis is performed by removing blood from the patient through an effluent or egress catheter tube, processing the removed blood through an artificial kidney machine to filter impurities from the blood, and returning the cleansed or processed blood to the patient through an influent, infusion or ingress catheter tube. The two catheter tubes may be any of several configurations, including but not limited to two essentially separate catheter tubes, a dual lumen catheter or any other suitable egress/ingress arrangement.
It is desirable to limit the number of times a vessel of the patient is penetrated for placement therein of dialysis catheter tubes. Accordingly, once placed, it is desirable for the distal end of the egress and ingress catheter tubes to be left indwelling for an extended period of time to accommodate spaced, repeated dialysis. Accordingly, the indwelling egress and ingress catheter tubes are inactive typically for much longer intervals than they are active. In addition, catheter tubes for other purposes are sometimes left indwelling for long periods of time and are frequently idle with no flow therethrough. This includes, but is not limited to, the central venous catheter category.
During idle times, when flow is not occurring in a given indwelling catheter tube, blood tends to enter the distal opening of the indwelling catheter tube. This is true even when the lumen of the catheter tube is full of liquid, other than blood, such as saline or heparin. During these idle times, blood flow through the vessel around the outside of the catheter tube tends to evacuate liquid from the lumen at the distal tip of the idle indwelling catheter tube, which is replaced by blood. This blood in the distal tip of each catheter tube tends to remain stationary, risking the development of a clot.
When clotting occurs within the lumen at the distal end of a catheter tube, an expensive clotbusting medication, such as Urokinase, is introduced into the proximal end of the catheter tube. After a suitable waiting period, during which the clot is softened, the medication and softened clot are aspirated from the catheter tube through the proximal end thereof. Where sufficient softening does not occur, the expensive clot-busting medication process may be repeated. Sometimes the clot is discharged into the vessel from the lumen using a liquid under positive pressure, which creates undesired risks for the patient. If all else fails, the catheter tube with the clot therein is removed from the patient at the vessel puncture site and a new replacement catheter tube inserted into the vessel.
Given the foregoing, provision of reliable and inexpensive methods and apparatus for avoiding or greatly alleviating clotting in indwelling catheter tubes would solve a long standing medical problem.